CIVIL ENGINEERING DEPT. Geotechnics and applied geology TOPIC : TYPES OF ROCKS AND ITS PROPERTIES NAMEENROLLMENT NO EKTA PATEL HARPIK PATEL RUSHIN PATEL ZANKHIL PATEL PRANAV PATEL DEEPAK PUNJABI

The diagram in the next slide represents the ROCK CYCLE—a scheme that represents the processes of continuous changes that connect the three major groups of rocks: SEDIMENTARY IGNEOUS METAMORPHIC It also shows two other important parts of the “Rock Cycle” – SEDIMENTS and molten LAVA and MAGMA Note about image sources: Many images come from a website (Volcano World) that no longer is supported, so no credit is given. The last slide provides possible sources.

Here is another version of the Rock Cycle

IGNEOUS ROCKS  Form by solidification (crystallization) of melted minerals  At the surface, LAVA hardens to form EXTRUSIVE rocks with tiny (FINE- GRAINED) crystals or GLASSY (no crystal) TEXTURES  Beneath the surface, MAGMA hardens to form INTRUSIVE rocks with easily visible (COARSE-GRAINED) crystal texture.

Granite  Light-colored, coarse- grained, no pattern  Mostly quartz, feldspar, mica, and hornblende  Often used for buildings and monuments

Basalt  Dark-colored, fine- grained, extrusive  Formed where lava erupted onto surface  Most widespread igneous rocks  Found locally in the Palisades along west shore of Hudson River, Connecticut River valley

Gabbro  Dark-colored, coarse- grained intrusive  Similar composition to basalt— plagioclase feldspar with some pyroxene and olivine

Obsidian  Natural volcanic glass  Forms when lava cools very quickly  Usually dark, but small pieces may be clear  Fractures along curved (conchoidal) surface  Used as spear and arrow points, knives

Pumice and other igneous rocks  Light colored, frothy (many air spaces)  Same minerals as in granite, but finer in grain size

Sedimentary Rocks Sedimentary rocks may be made of rock fragments— sediments—or by chemical reactions. The classification of sediments is shown below.

Clastic rocks–made of cemented sediments— are classified by their grain sizes.

Non-clastic rocks form by chemical precipitation (settling out from a solution.) Limestone is made from calcite, chert from quartz, and halite is rock salt.

Biologic sedimentary rocks come from the remains of organic matter.  The most important of these is coal. Anthracite coal results from the greatest pressure and releases the most energy when burned. Other varieties are bituminous and lignite. “Petrified” (permineralized) wood is another organic rock.

More about sedimentary rocks  Shale is the most common sedimentary rock  Sedimentary rocks cover about three- quarters of the land surface  For more about sedimentary rocks:

Properties Colour The colour of a sedimentary rock is often mostly determined by iron, an element with two major oxides: iron(II) oxide and iron(III) oxide.. Iron(II) oxide only forms under anoxic circumstances and gives the rock a grey or greenish colour. Iron(III) oxide is often in the form of the mineral hematite and gives the rock a reddish to brownish colour. In arid continental climates rocks are in direct contact with the atmosphere, and oxidation is an important process, giving the rock a red or orange colour. Thick sequences of red sedimentary rocks formed in arid climates are called red beds. However, a red colour does not necessarily mean the rock formed in a continental environment or arid climate.ironiron(II) oxideiron(III) oxideanoxichematitered beds

The presence of organic material can colour a rock black or grey. Organic material is in nature formed from dead organisms, mostly plants. Normally, such material eventually decays by oxidation or bacterial activity. Under anoxic circumstances, however, organic material cannot decay and becomes a dark sediment, rich in organic material. This, can for example, occur at the bottom of deep seas and lakes. There is little water current in such environments, so oxygen from surface water is not brought down, and the deposited sediment is normally a fine dark clay. Dark rocks rich in organic material are therefore often shalesdecaysshales

Texture The size, form and orientation of clasts or minerals in a rock is called its texture. The texture is a small-scale property of a rock, but determined many of its large-scale properties, such as the density, porosity or permeability.sizetexturedensityporositypermeability Clastic rocks have a 'clastic texture', which means they consist of clasts. The 3D orientation of these clasts is called the fabric of the rock. Between the clasts the rock can be composed of a matrix or a cement (the latter can consist of crystals of one or more precipitated minerals). The size and form of clasts can be used to determine the velocity and direction of current in the sedimentary environment where the rock was formed; fine, calcareous mud only settles in quiet water, while gravel and larger clasts are only deposited by rapidly moving water. The grain size of a rock is usually expressed with the Wentworth scale, though alternative scales are used sometimes. The grain size can be expressed as a diameter or a volume, and is always an average value - a rock is composed of clasts with different sizes. The statistical distribution of grain sizes is different for different rock types and is described in a property called the sorting of the rock. When all clasts are more or less of the same size, the rock is called 'well-sorted', when there is a large spread in grain size, the rock is called 'poorly sorted'.fabricmatrixcurrentcalcareous mudWentworth scalestatistical distributionsorting

The form of clasts can reflect the origin of the rock. CoquinaCoquina, a rock composed of clasts of broken shells, can only form in energetic water. The form of a clast can be described by using four parameters: Surface texture describes the amount of small-scale relief of the surface of a grain that is too small to influence the general shape. rounding describes the general smoothness of the shape of a grain.rounding 'Sphericity' describes the degree to which the grain approaches a sphere.Sphericitysphere 'Grain form' describes the three dimensional shape of the grainGrain form Chemical sedimentary rocks have a non-clastic texture, consisting entirely of crystals. To describe such a texture only the average size of the crystals and the fabric are necessary.

Mineralogy Most sedimentary rocks contain either quartz (especially siliciclastic rocks) or calcite (especially carbonate rocks). In contrast with igneous and metamorphic rocks, a sedimentary rocks usually contains very few different major minerals. However, the origin of the minerals in a sedimentary rock is often more complex than those in an igneous rock. Minerals in a sedimentary rock can have formed by precipitation during sedimentation or diagenesis. In the second case, the mineral precipitate can have grown over an older generation of cement.A complex diagenetic history can be studied by optical mineralogy, using a petrographic microscopequartzsiliciclasticcalcitecarbonate rocksoptical mineralogypetrographic microscope

Carbonate rocks dominantly consist of carbonate minerals like calcite, aragonite or dolomite. Both cement and clasts (including fossils and ooids) of a carbonate rock can consist of carbonate minerals. The mineralogy of a clastic rock is determined by the supplied material from the source area, the manner of transport to the place of deposition and the stability of a particular mineral. The stability of the major rock forming minerals (their resistance to weathering) is expressed by Bowen's reaction series. In this series, quartz is most stable, followed by feldspar, micas, and other less stable minerals that are only present when little weathering has occurred.The amount of weathering depends mainly on the distance to the source area, the local climate and the time it took for the sediment to be transported there. In most sedimentary rocks, mica, feldspar and less stable minerals have reacted to clay minerals like kaolinite, illite or smectite.carbonatecalcitearagonitedolomiteooidsBowen's reaction seriesfeldsparmicasclay mineralskaoliniteillitesmectite

Metamorphic Rocks  Formed by heat and pressure changing existing rocks  REGIONAL METAMORPHIC affects a large area and results from plate tectonics  CONTACT METAMORPHISM affects rocks on a local scale, such as “baking” sedimentary rocks next to magma or lava

“Foliated” rocks contain much mica and other rocks that produce layering or banding Gneisses and schists are common in New York City and Westchester.

Non-foliated metamorphic rocks include marble, which comes from limestone, and quatzite, which comes from sandstone

Locations, types, and ages of the bedrocks are represented in a geologic map

THANK YOU